CHARLESTON, S.C — Bernie Sanders is heading into South Carolina on Saturday, the state that broke him in 2016, stronger than ever after a razor-thin second place finish in Iowa and wins in New Hampshire and Nevada.

"I just think there's one big, huge, screaming story here tonight, and that is that there is a frontrunner in the 2020 Democratic presidential race," veteran Democratic strategist James Carville, a vocal Sanders critic, said of the Vermont senator on MSNBC. "We're in a whole new ballgame here and...some of these candidates are going to have to make really hard decisions about who stays in and who gets out and where we go from here."

But the heat will be on like never before for the self-described democratic socialist as his doubters and detractors scramble to try to stop him and the race's one-time frontrunner, Joe Biden, tries to reclaim that position with a second-place showing in Nevada and a promise to win South Carolina.

"We're alive, we're coming back, and we're going to win," Biden told supporters at a union hall in Las Vegas. "I ain't a socialist. I ain't a plutocrat. I'm a Democrat — and proud of it."

South Carolina's Saturday primary will come just four days before Super Tuesday, March 3, when some 40 percent of the delegates in the entire primary contest are up for grabs.

Many candidates skipped out of Nevada early to campaign in places like Texas, California and Washington, and they'll use South Carolina to hit East Coast Super Tuesday states like Virginia and North Carolina.

Four years ago, Nevada halted Sanders' momentum and South Carolina reversed it when Hillary Clinton crushed him here, exposing a weakness with voters of color that would prove fatal to his 2016 presidential campaign.

But years of organizing and a re-tooled message are bearing fruit for Sanders.

He handily won Latinos in Nevada, where his campaign was advertising on Spanish-language radio and to Latin music listeners on Spotify for months, and he came in a close second to Biden among African-Americans, according to NBC News entrance polls.

In South Carolina, where African-Americans will make up a majority of Democratic electorate in Saturday's primary, the commanding 20 percentage point lead Biden enjoyed last fall has been whittled down to a less than four points over Sanders now in polling averages

Clay Middleton, a Democratic strategist who ran Clinton's campaign in South Carolina, was planning to vote early for Biden two weeks ago — but then decided to hold off. "I don't know what it was, it just didn't feel right," he said.

Now he wants to wait and see what happens in Tuesday's debate here. "I'm undecided," he said, "my wife is undecided. My immediate family and good friends are all undecided."

That could spell trouble for Biden in a state that is supposed to be his firewall and focuses attention on his performance in the upcoming debate.

Still, Antjean Seawright, a Columbia-based Democratic consultant, said the state remains Biden's to lose. "I think this is honestly a race for second place," he said.

That competition is likely between Sanders and California billionaire Tom Steyer, who has been a non-factor in other states and didn't qualify for last week's debate in Las Vegas but is polling in third place here, just behind Sanders.

Other campaigns have largely written off South Carolina, given Biden's perceived strength, but Steyer has invested heavily here and in outreach to African-Americans elsewhere. He came in third among black voters in Nevada, even though he's polling at just 2 percent among all Democrats nationally.

"I can't see how Steyer justifies staying in after getting zero delegates in the first three states," said Brady Quirk-Garvan, the former chairman of the Charleston Democrats. "At this point, moderate candidates who don't see a path to win but are staying in are just helping to create a Sanders nominee and that scares a lot of South Carolinian Democrats."

Many red-state Democrats are worried that Sanders would make it impossible for the party to win in more conservative states like this one.

But the rest of the field is splintered and shows no signs of going anywhere before Super Tuesday and making it more likely that Sanders will be the only candidate to consistently cross the 15 percent threshold needed to win delegates in upcoming contests.

One big wildcard is whether billionaire former New York City Mayor Michael Bloomberg will start running negative ads against Sanders. So far, he's attacked only President Donald Trump. But some Democrats say massive spending from Bloomberg is the only thing that could stop Sanders now for the nomination.

Asked about the possibility after last week's debate, Howard Wolfson, a top Bloomberg adviser, said the campaign had no immediate plans, but added, "Campaigns are fluid, we'll see."